PhosphoSite(r) and the Phosphoproteome of Cancer Protein kinases and their substrates are important regulators of signal transduction pathways during normal growth and development as well as during oncogenesis. PhosphoSite is a bioinformatics resource that systematically has collected information from thousands of published reports about specific phosphorylation sites, how they are physiologically regulated, and the biological consequences of these phosphorylation events. PhosphoSite(r) was designed primarily to curate and present information from published literature, which historically focused on one or a few phosphorylation sites;curation and organization of this information was relatively simple. Using tandem mass spectrometric methodologies, the CST Cancer Biology Group and others are discovering thousand of new phosphorylation sites in human cancers which must be processed and uploaded into PhosphoSite(r). We propose to significantly reengineer PhosphoSite(r) to accommodate this abundance of data and to update the interfaces so that users can view and compare sets of phosphorylation sites associated with specific cancers and other diseases. We also propose to develop the capacity to transfer data from PhosphoSite(r) into pathway visualization programs that allow users to explore the rich regulatory interactions that are described in PhosphoSite(r). PhosphoSite(r) and the Cancer Phosphoproteome Project Narrative The PhosphoSite(r) database catalogs modification of proteins by attachment of a phosphate group - a change that can affect many cellular processes, including the transition from normal cell to cancer cell. We are improving PhosphoSite(r) so that it can accommodate the vastly increased number of phosphate modifications now being discovered. We will also release modifications discovered in our laboratories to the scientific community to further its understanding of cellular changes leading to cancer.